This invention relates generally to metal joining processes and more particularly to an improved method for interjoining multiple stranded wire cable ends by providing a solid metal junction therebetween having the same circumferential configuration and equivalent cross-sectional area of the parent cables and selected strength factors.
In the manufacture of wire, particularly electrical conductor wire made from non-ferrous materials such as aluminum, copper and their common conductor alloys, the manufacturer is confronted with the serious problem of interjoining the terminal ends of wire sections to form continuous lengths or runs. Such junction problem is usually encountered during continuous wire drawing and coating operations wherein wire diameters and cross-sections are reduced in size or surface coating materials applied thereabout to achieve a finished wire product preferably having continuity of form, electrical conductivity and strength and from which finite lengths are cut for sale to the customer or futher processing.
In my prior U.S. Pat. No. 3,828,601 issued Aug. 13, 1974, an apparatus and method for effecting junctions between the ends of solid metal wire sections are described. Briefly, as therein taught, the method utilizes two basic procedures, namely, interjoining solid wire ends by thermal butt welding techniques to insure a true metallurgical bond therebetween, and mechanically upsetting and cold working the welded joint and bond zone to remove the heat affected metal of the joint and to provide a junction interface between the individual solid wires having at least the original metallurgical and physical properties of the parent cable metal.
When such individual wires are fabricated into more complex products, such as stranded wire electrical conductor cables, a number of spools of wire are loaded in a stranding machine where they are continuously twisted and formed into multi-wire cables. As this stranding process proceeds, the terminal end of each individual wire must be joined to the starting end of a new spool of wire without interrupting the process. While the teachings set forth in my aforesaid patent are highly successful for the purposes of interjoining such opposing ends of the individual solid metal wires, in the above outlined cable making process, such teachings are not correspondingly immediately applicable to the interjoining of the multiple strands at the cable ends.
In the first instance, in contrast to the relative ease of effecting a good molecular interjunction between individual solid metal wire ends by normal electric butt welding procedures for instance, use of heat and pressure for interjoining the multiple strand cable end is generally unsuccessful. This failure is principally due to the excessive oxidation of the individual cable strands during the normal butt welding operations and the further tendency of the wire strands to radially bulge and separate under axial load. Thus the end result of an attempted butt welding and cold upsetting of opposing multiple strand cable ends is generally unreliable, inconsistent and productive of a highly oxidized bond zone which is very brittle and practically devoid of the desired metallurgical and physical properties of the parent cables. Consequently cables so joined are not ideally suited to further operations of the cable fabricating processes such as extruding an insulating coating thereover, since such joints or junctions lack the necessary strength and ductility to withstand the applied pulling forces and are easily broken. Any breakage of the cable during such continuous insulation applying operations, for example, is time consuming, dangerous and expensive, and may damage the production equipment to an extent requiring costly shut down of the entire production line.
By current practice, cable joints formed by known welding, brazing, friction welding, cold upsetting and other known techniques, frequently fail to meet necessary quality and strength specifications and usually must be removed from the completed cable and scrapped, leading to economic loss of both material and man hours. In other instances, such joints as are acceptable often fail in use, requiring costly onsite or field repairs.
As a result of the foregoing briefly outlined difficulties, the interjoining of stranded wire cable ends is and has been a major production and economic burden in the wire making industry, heretofore defying successful solution.
In brief, my present invention advances and adopts certain of the basic teachings and concepts found in my aforesaid prior patent to a successful method for the interjunction of stranded wire cable ends. To this end, I have discovered that if the end of a multi-strand conductor cable is first thermally bonded to a solid metal junction section made of the same material as the conductor strands, such as aluminum, copper, and their common conductor alloys, two such solid metal junction sections may be successfully and conveniently bonded by electrical butt welding techniques. Thereafter the welded joint area of the solid metal junction sections and heat affected zones adjacent thereto may be mechanically cold worked, formed and removed to produce a satisfactory solid metal interface or joint section between two cable ends. Moreover, the degree of cold working and forming of the junction section and adjacent areas of the stranded cables may be selectively controlled to produce a joint area having the circumferential configuration and cross-sectional area of the parent cables and selected strength properties.
It is an important object of this invention to provide a new and improved method of interjoining ends of stranded wire cables.
It is a further object of this invention to provide an improved method, as aforesaid, in which the junction between the joined cables comprises a true metallurgical bond having selectively controlled metallurgical and physical properties.
It is another object of this invention to provide an improved method of interjoining stranded wire conductor cable ends in which the resulting junction or joint area has the circumferential configuration and cross-sectional area of the joined parent cables.
Having thus described my invention, the above and further objects, features and advantages thereof will be understood from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings, as representing the best mode presently known to enable those skilled in this art to practice its teachings.